1. Field of Invention
The present invention relates to an apparatus for driving a light source for a display device.
2. Description of Related Art
There are various types of display devices that are commonly used for computers and television sets. The types of display devices include self-emitting displays such as light emitting diodes (LEDs), electroluminescence devices (ELs), vacuum fluorescent displays (VFDs), field emission displays (FEDs) and plasma panel displays (PDPs), and non-emitting displays such liquid crystal displays (LCDs). Unlike the self-emitting displays, the non-emitting displays require a light source.
An LCD includes two panels with field-generating electrodes and a liquid crystal (LC) layer with dielectric anisotropy interposed therebetween. The field-generating electrodes generate an electric field in the liquid crystal layer in response to applied voltages, and the transmittance of light passing through the panels varies depending on the strength of the electric field. The strength of the electric field is controlled by the applied voltages. Accordingly, desired images are displayed by adjusting the applied voltages.
The light source for an LCD may be an artificial light source that is installed in the LCD device or natural light. When using the artificial light source, the overall brightness of the LCD screen is usually adjusted by either regulating the ratio of “on” and “off” durations of the light source or regulating the current through the light source.
The artificial light source, which is part of a backlight assembly, is often implemented as a plurality of fluorescent lamps that are connected to a plurality of inverters for driving the lamps. The lamps may be disposed under an LC panel assembly, such as in a direct-type backlight assembly, or may be disposed along one or more edges of the LC panel assembly, such as in an edge-type backlight assembly. The inverter receives a DC (direct current) input voltage from an external device and converts it to an AC (alternating current) voltage, and then applies the voltage to the lamps to turn on the lamps and to control the brightness of the lamps. The voltage may be stepped up by a transformer prior to being applied to the lamps. The inverter also monitors a voltage related to a current flowing through the lamps and controls the voltage applied to the lamps based on the monitored voltage.
Accordingly, the artificial light source needs several peripheral devices such as inverters and sensors, which undesirably increase manufacturing cost. Aside from the associated cost increase, the peripheral devices are undesirable because they increase the volume and the weight of the backlight assembly, adversely affecting the mobility of the display device. Thus, a display device design that allows operation with fewer peripheral devices is desirable.